Press-formed product and method for designing the same

Abstract

A press-formed product is shaped by press-working from a tailored blank made up of a plurality of metal sheets butt-welded together. The press-formed product includes a flange section, and an arc-shaped area which is an area of the flange section which is formed by stretch flange deformation, and in which an inner peripheral edge is open. A weld line of the tailored blank intersects with the inner peripheral edge and an outer peripheral edge of the arc-shaped area. An angle θ formed by the weld line and a maximum principal strain direction of the stretch flange deformation is 17 to 84°.

The invention claimed is: 
     
       1. A press-formed product comprising a tailored blank made up of a plurality of metal sheets butt-welded together, wherein
 the press-formed product includes a flange section, and an arc-shaped area in which an inner peripheral edge is open in the area of the flange section, 
 a weld line of the tailored blank intersects with the inner peripheral edge of the arc-shaped area and an outer peripheral edge of the arc-shaped area, and 
 an angle formed by the weld line and a maximum principal strain direction is 17 to 84°. 
 
     
     
       2. The press-formed product according to  claim 1 , wherein an angle formed by the weld line and a tangential line of the inner peripheral edge at an intersection point between the weld line and the inner peripheral edge is 40 to 75°. 
     
     
       3. The press-formed product according to  claim 1 , wherein
 a number of the metal sheets for making up the tailored blank is two, and the two metal sheets are different from each other in at least one of tensile strength and sheet thickness. 
 
     
     
       4. The press-formed product according to  claim 3 , wherein
 the press-formed product is an automobile skeleton component which is curved in an L-shape along the longitudinal direction, the skeleton component having a hat-shaped cross section over an entire range in a longitudinal direction; 
 the skeleton component includes a curved region curved along the longitudinal direction, and a first region and a second region, respectively extending from both ends of the curved region, the skeleton component being supposed to be subjected to a collision load along an extended direction of the first region; 
 the arc-shaped area is a flange section on an inner side of curve of the curved region; and 
 a sheet thickness of the metal sheet disposed on the side of the first region is larger than a sheet thickness of the metal sheet disposed on the side of the second region. 
 
     
     
       5. The press-formed product according to  claim 4 , wherein
 the skeleton component is a front pillar lower-outer, and 
 the first region is coupled to a side sill, and the second region is coupled to a front pillar upper. 
 
     
     
       6. The press-formed product according to  claim 4 , wherein
 a difference between a multiplication value of a tensile strength and a sheet thickness of the metal sheet disposed on the side of the first region, and a multiplication value of a tensile strength and a sheet thickness of the metal sheet disposed on the side of the second region is not more than 600 mm·MPa. 
 
     
     
       7. A method for designing the press-formed product according to  claim 1 , the press-formed product being shaped by press working from a tailored blank made up of a plurality of metal sheets butt-welded together, wherein
 the press-formed product includes a flange section, and an arc-shaped area which is formed by stretch flange deformation and in which an inner peripheral edge is open, in the area of the flange section, in which a weld line of the tailored blank intersects with the inner peripheral edge of the arc-shaped area and an outer peripheral edge of the arc-shaped area, and wherein 
 when designing the press-formed product, the weld line is disposed such that during press working, a relative difference between strain dε WL y′ in a direction along the weld line at a center in a width direction of the weld line, and strain dεy′ in a direction along the weld line in the vicinity of the weld line of the metal sheet is not more than 0.030. 
 
     
     
       8. The method for designing a press-formed product according to  claim 7 , wherein
 the relative difference between strain dε WL y′ and strain dεy′ is 0.